This is really a fun and awesome setup. You can modify your VTEC engagement point, fuel cutoff point, and tune your fuel/ignition maps.
You can even make your money back by tuning your friends' cars and such.

i'm not sure if you are familiar with chipping a p28 but, you have to put a jumper wire across two solder joints in order for it to read the external ROM. By wiring a switch in it's place, you can easily choose between internal (stock) and external ROM's for such reasons like emissions and gas mileage.